6. Notes from the Workshop Sessions (afternoon)
The following issues and suggested actions have been collated from the contributions to the workshop sessions:
6.1 ISSUES OF DEFINITION
Definition of Scottish peat land?
Accept that it is areas with an organic horizon of over 50cm.
Are we concerned solely with the state and condition of the soil?
Accept that in terms of a peat land ecosystem the state and condition relate to vegetation, soil and water.
6.2 DETERMINING THE CORE REQUIREMENTS
What we are trying to detect, measure or monitor and what the ultimate purpose is?
Appear to agree that we are aiming to measure both extent (geographical extent) and the severity which implies monitoring dynamics and especially the flux of carbon lost from erosional gully systems.
6.3 WHAT DO WE NEED TO MEASURE?
Extent of peat land vegetation and its condition ( UKBAP)
Form, depth and connectedness of erosion gullies
Area of bare peat
Mass fluxes: mass leaving peat lands over time
Accept it is not possible to assess and measure all of these on a national basis. Strong support for a hybrid or multi-layered approach which includes an assessment of extent at a national level (this could be based on a revisiting of the University of Stirling sampling methodology with a combination of satellite imagery and aerial photography) and an element of monitoring based on a representative sample of sites which recognise the key role of hydrological drivers (possibly using sub-catchments as the basic sampling unit?). The monitoring component would require high resolution data and could be made more useful if connected to a field monitoring effort ( e.g. of stream water DOC).
6.4 HOW DO WE MEASURE THESE?
STEP 1. Creation of a national peat land database. Be aware of and collate (as far as possible into a GIS) the existing knowledge on the extent of peat land erosion in Scotland. . This should include:
- Where the peat is >50cm (soil map)
- Peat Survey maps
- Peat land vegetation/ land cover from 1988 (not = peat) with erosional features.
- SBBI based on Landsat TM
- Land Cover Map 2000
- National Countryside MS ( SNH)
- University of Stirling study data
- Lewis and Harris & Shetland
- Methods: JNCC 2004 "Remote sensing of bog surfaces"
- National Soil Inventory of Scotland
- Condition Assessments for Designated Sites ( SSSIs, SACs) from field data
STEP 2 Mapping the likelihood of erosional features across Scotland. Use the knowledge in the national peat land database concerning the geography of erosional sites to develop a first (probabilistic) approximation of the extent of eroded peat land across Scotland.
STEP 3 Refining the national estimates. Using the national map derived in step 2 above, identify areas that have a high likelihood of erosional features from existing knowledge. Develop and apply a stratified random sampling approach (similar to that adopted by University of Stirling approach) and map selected sites using high resolution satellite imagery and/or digital aerial photography. Guidance on spatial resolution of imagery includes the "jump test" (must be able to identify those gullies that you can jump across!) 2m is best and 5m is marginal. Wider habitat information can be derived from 4-8m resolution data. Be aware of tasking costs and acceptable cloud cover in relation to pay-to-point systems like IKONOS and QUICKBIRD and potential use of pan-sharpened MS data and data from the TOPSAT 2.5m experimental satellite
STEP 4 Estimating severity of erosion. Develop a system that is based upon a low risk data source. Given the fact that it offers an opportunity to look-back over 50 years, orthorectified aerial photography appears to be the most appropriate candidate for this. Lidar offers some potential for the future. Critical to create measurement protocols based upon understanding of peat erosional systems (such as that provided by the work of Margaret Bower and refined by Evans, Warburton et al.). Critical measurements are the length and depth of gully systems, gully connected-ness (topology) and extent of re-vegetation in gullies. IF the sites for this detailed monitoring could be dovetailed with other monitoring networks ( e.g. The Environmental Change Network), then other relevant flux measures could be incorporated ( e.g.DOC). [Consideration might also be given to how this fits within any overall plan for a soil monitoring framework in Scotland].